JP4385129B2 - Method for producing molecularly aligned nanophotonic crystal device - Google Patents

Description

  The present invention is a molecular array type nanophotonic crystal device suitable for various fields including a polarizer, LED, DFB laser, DBR laser, resonant filter, optical waveguide, optical circuit, optical fiber, optical deflection, prism, etc. And a molecular arrangement type nanophotonic crystal device.

In recent years, nanotechnology has attracted a great deal of attention as the key to its solution in many fields such as information technology, biotechnology, medical care, energy problems, and environmental problems.
In this nanotechnology field, photonic crystals are particularly attracting attention. A photonic crystal is an artificial multidimensional periodic structure that combines two or more media with different dielectric constants, and is called a “crystal” because its structure and properties are similar to a solid crystal. Is. Various uses and applications are considered for photonic crystals, and their research has been extensively performed recently.

  The present inventors have disclosed a microresonator structure corresponding to a one-dimensional photonic crystal device in which substances having a sufficiently stable absorption band at room temperature, such as a J-aggregate, are arranged with spatial regularity. (Japanese Patent Laid-Open No. 2002-328350). However, in the microresonator structure of the previous application, no consideration was given to the orientation of molecules in a J aggregate or the like embedded in a groove constituting the microresonator.

JP 2003-195001 A JP 2002-328350 A

By aligning the molecular orientation, the optical anisotropy characteristics of the photonic crystal device are expected to be improved, and the effect of increasing the stability of the material is expected.
The effect of aligning molecular orientation has been recognized in the past, but when introducing a molecular array type nanophotonic crystal such as a J-aggregate into a submicron-scale structure, the alignment of nanometer-sized molecules is aligned in one direction. It was difficult to control the molecular arrangement.

Accordingly, an object of the present invention is to provide a method for producing a molecular arrangement type nanophotonic crystal device in which the orientation of molecules of the J aggregate is aligned in the longitudinal direction of the groove by adding an annealing process to the conventional process. And
Another object of the present invention is to provide a molecular arrangement type nanophotonic crystal device manufactured by the above manufacturing method.

The present invention includes a step of forming a plurality of elongated grooves at periodic intervals on a substrate, a step of embedding pseudoisocyanine in the grooves, and maintaining the temperature of the substrate at 35 ° C. to 40 ° C. and the length of the grooves An object of the present invention is to provide a method for producing a molecular array type nanophotonic crystal device comprising a step of annealing by spraying a gas containing water vapor along a direction .

  In the present invention, since the molecular arrangement can be controlled by controlling the temperature, the atmospheric gas, the flow rate, and the directionality thereof, it is possible to provide a molecular arrangement type nanophotonic crystal device having good characteristics with uniform molecular arrangement.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1A is a perspective view schematically showing an example of a molecular arrangement type nanophotonic crystal device according to the production of the present invention.
FIG.1 (b) is the bb sectional drawing. Here, for convenience of the polarization direction, the x, y, and z directions are displayed in FIG. In FIG. 1B, the y direction corresponds to the vertical direction of the paper and the longitudinal direction of the groove. The x direction is a direction intersecting with the groove, and the thickness direction of the substrate corresponds to the z direction.

A bulk material such as a quartz substrate is cut by lithography or etching to form a plurality of elongated grooves with spatial regularity.
Next, the J aggregate is embedded in the groove. The molecular orientation of the embedded J aggregates is not aligned in one direction here.
Next, the embedded J aggregate is annealed.
The annealing treatment referred to in the present invention refers to a treatment performed by controlling the temperature, the atmosphere gas, its flow rate and directionality so that the molecular arrangement of the J aggregates moves and the molecular orientation is aligned in one direction.

  FIG. 2 is a partially enlarged conceptual diagram showing a molecular arrangement type nanophotonic crystal structure and its molecular orientation. FIG. 2 schematically shows that molecules of a J aggregate (pseudoisocyanine) are arranged in a space of several hundred nanometers in the direction of the length of the groove.

A molecular arrangement type nanophotonic crystal structure using pseudo-isocyanine (PIC) J aggregate will be described in detail.
A plurality of elongated grooves are formed in a quartz glass substrate with a width of 210 nm, a depth of 400 nm, and spatial regularity at intervals of 420 nm to constitute a diffraction grating.
Next, a solution in which pseudo-isocyanine molecules are dissolved in methanol is prepared, spin-coated on a quartz glass substrate, and embedded in the groove to obtain a nanophotonic crystal structure.
The step of embedding the pseudoisocyanine molecules in the groove is to replace the spin coating on the quartz glass substrate with the quartz glass substrate standing vertically and pouring the solution into a cast film or beaker that flows the solution along the groove. A technique such as dip coating that immerses and pulls up vertically may be used.

Finally, an annealing process is performed on the photonic crystal structure.
In the annealing treatment, a nitrogen gas containing water vapor is caused to flow along the longitudinal direction of the groove as indicated by an arrow for several tens of seconds on a photonic crystal substrate maintained at 35 ° C. to 40 ° C. In this case, the water vapor concentration was about 10% or less.
Through the above steps, a molecular arrangement type nanophotonic crystal device having a crystal structure in which pseudo-isocyanine molecules are aligned in the longitudinal direction of the groove is completed.

  Here, the quartz glass substrate needs to have a clean surface. It is also effective to make the molecules easy to move by performing a surface treatment considering the compatibility with the molecules. In the case of the pseudoisocyanine molecule, the compatibility with water is good, and the clean surface on the quartz glass substrate is hydrophilic, so that the molecule is easy to move.

The mechanism for obtaining a photonic crystal device in which pseudo-isocyanine molecules are aligned by annealing treatment is considered as follows.
Although the solubility of pseudo-isocyanine molecules in water is quite low, it is well known that crystal water is contained when pseudo-isocyanine molecules are solidified into crystals. In other words, water does not go until the pseudo-isocyanine molecule itself is dissolved and moved, but it contributes to the movement of the molecular arrangement by incorporating water, and this just balances the annealing temperature of 35 ° C to 40 ° C. Therefore, the molecular arrangement along the longitudinal direction of the groove was realized because the molecular arrangement moved and the direction of gas flow coincided with the longitudinal direction of the groove of the one-dimensional photonic crystal.

FIG. 3 is a view for verifying the effect of the annealing process on the one-dimensional photonic crystal structure. The change in the transmission spectrum before and after annealing is shown with and without the photonic crystal structure. FIG. 3 at the bottom of FIG. 3 shows the effect of the annealing process according to the present invention. For the photonic crystal in which pseudo-isocyanine molecules are aligned, the annealing process using the one-dimensional photonic crystal structure performed as an example of the present invention is performed. The front and back transmission spectra are shown.
When there is a diffraction grating (one-dimensional photonic crystal structure), a strong resonator mode is observed near 620 nm as a decrease in transmitted light (E // y).

The absorption band near 580 nm is the lowest exciton band peculiar to pseudoisocyanine and does not depend on the presence or absence of a diffraction grating (one-dimensional photonic crystal structure).
It is known that the absorption band has absorption only in the arrangement direction of molecules / molecular aggregates.
Comparing the E // x transmission spectra in the absorption band before and after annealing, what was about 0.3 before the annealing treatment is about 0.45 after the annealing treatment.
Therefore, it can be seen that the molecular arrangement in the x direction is reduced, and the molecular arrangement in the y direction is remarkably improved as compared with that before the annealing treatment.
This indicates that the long axes of the molecules are aligned in the y-axis direction of the one-dimensional photonic crystal.

  For comparison, when there is no photonic crystal structure, that is, a solution in which pseudoisocyanine molecules are dissolved in methanol without forming a groove is prepared, and this is spin-coated on a quartz glass substrate. Is shown in FIG. In this case, the transmission spectrum does not change before and after the annealing treatment, and there is no difference between E // x and E // y, and both are about 0.1. This indicates that the major axes of the pseudoisocyanine molecules are aligned without aligning the directions.

  From the above, it can be seen that adding an annealing process to the photonic crystal structure is effective in utilizing the photonic crystal structure as a device.

As mentioned above, although preferable embodiment and an Example were described, this invention is not limited to this, In the range which does not deviate from the summary of this invention, an appropriate change is possible.
In other words, a quartz glass substrate has been described as an example of the substrate, but a glass substrate other than quartz glass may be used. In the embodiment, a transparent glass substrate is used to obtain a transmission spectrum, but a semiconductor substrate such as silicon is used. May be.

Although pseudo isocyanine was illustrated, it is not restricted to this, It is applicable about the J aggregate of other molecular crystals.
The annealing conditions at this time are such that the solvent that moves the molecular arrangement like water for the PIC molecules is changed for each J aggregate, and the temperature / atmosphere gas is adjusted so that the molecules of the J aggregate are aligned in one direction.・ Determine in consideration of the flow rate and directionality.

In addition to light emitting elements and lasers, they are related to integrated optical elements such as optical waveguides / branches and optical modulators, and can be used in parts that require molecular alignment.
Furthermore, it is expected that optical devices utilizing optical anisotropy (such as wavelength conversion using polarizers and phase matching) will be applied to integrated devices by aligning molecular orientation.

It is a perspective view which shows a photonic crystal device typically. It is bb sectional drawing of a photonic crystal device. It is the conceptual diagram which showed the one-dimensional photonic crystal structure and molecular orientation as an Example of this invention. FIG. 3 is a transmission spectrum diagram of a molecular assembly in a one-dimensional photonic crystal according to the present invention.

Explanation of symbols

1 Quartz glass substrate 2 Elongated groove
3 Nitrogen gas containing water vapor 4 Pseudoisocyanine

Claims (1)

Forming a plurality of elongated grooves at periodic intervals on the substrate, embedding pseudoisocyanine in the grooves, and maintaining the temperature of the substrate at 35 ° C. to 40 ° C. along the longitudinal direction of the grooves The manufacturing method of the molecular arrangement type | mold nanophotonic crystal device characterized by including the process of annealing-treating by spraying the gas containing water vapor | steam .